Hot water supply device

ABSTRACT

A hot water supply device ( 1 ) includes: a fin and tube type heat exchanger ( 17 ) for aplying heat to water with combustion gas; a temperature detection means ( 32 ) for detecting an exhaust temperature after heat exchange by the heat exchanger ( 17 ); and a determination means that determines that scale is deposited within the heat exchange tubing ( 27 ) of the heat exchanger ( 17 ) if the exhaust temperature detected by the temperature detection means ( 32 ) is higher than a set temperature.

BACKGROUND TECHNOLOGY

The present invention relates to a hot water supply device, and more particularly relates to a hot water supply device that is endowed with a function of determining whether or not clogging by scale is taking place due to scale having been deposited inside heat exchange tubing of a heat exchanger.

From the prior art, various hot water supply devices that utilize various sources of heat have been widespread in general household use, such as gas powered hot water supply devices, electrically powered hot water supply devices, and hot water supply devices that employ fuel oil and so on. In particular, a gas powered hot water supply device typically includes an air blower fan that intakes air for combustion from the exterior, a burner unit that mixes and combusts together the air for combustion and fuel gas, a heat exchanger that supplies heat to water by exchanging heat between the high temperature combustion gases and water flowing in a heat exchange tubing, an exhaust tube for discharging the exhaust after heat exchange to the exterior, and so on.

As the heat exchanger described above, generally a heat exchanger of the fin and tube type is employed including a heat exchange tubing and a plurality of fins that are fixed to this heat exchange tubing so as to be capable of heat transfer, and such heat exchangers in which the heat exchange tubing and the fins are made from copper material are in widespread use.

However, if tap water whose hardness is high is used as the fresh water that is supplied to the heat exchanger described above, then scale is separated out because of calcium and magnesium and so on included in the tap water combining with carbon dioxide ions or sulfuric acid ions or the like. When the temperature of the hot water becomes high, it becomes easier for the scale to be separated out, and clogging by scale may occur due to scale being deposited inside the heat exchange tubing of the heat exchanger, so that the problems occur that the heat exchange efficiency of the heat exchanger is deteriorated, and that the temperatures of the heat exchange tubing and of its fins become elevated.

If the use of the hot water supply device is continued in the state in which the clogging by scale has occurred, then the heat exchanger may be repeatedly subjected to thermal stress, and there is a fear that the heat exchanger may be damaged due to cracking at the junction portions between the heat exchange tubing and the fins. If this clogging by scale has occurred, it is necessary to eliminate the scale, and thus, from the prior art, hot water supply devices have been endowed with the functions of detecting clogging by scale and also of avoiding damage even if clogging by scale has occurred.

The following four publications are picked up as prior art documents.

-   Patent Document #1: Japanese Patent Publication 4,854,020. -   Patent Document #2: Japanese Laid-Open Patent Publication     2008-215657. -   Patent Document #3: Japanese Patent Publication 5,370,807. -   Patent Document #4: Japanese Patent Publication 3,907,032.

For example, in Patent Document #1, a device is disclosed that determines whether or not clogging by scale has occurred on the basis of elevation of the temperature of the warm water due to after-boiling after combustion has stopped. And, in Patent Document #2, a hot water heating device is disclosed that determines whether or not clogging by scale has occurred on the basis of variation of the heat exchange efficiency of the heat exchanger. Moreover, in Patent Document #3, a hot water supply device is disclosed that estimates the temperature of the combustion exhaust gas from which sensible heat has been recovered by the use of a combustion exhaust gas temperature estimation means, and that, even if the estimated temperature of the combustion exhaust gas has become elevated due to clogging by scale, while avoiding damage to the heat exchanger by performing combustion control so that the estimated temperature of the combustion exhaust gas does not exceed a predetermined temperature or by stopping combustion, also notifies the user of the occurrence of clogging by scale. Furthermore, in Patent Document #4, a hot water supply device is disclosed that performs combustion control so that the temperature of warm water within a heat exchanger that absorbs latent heat of the combustion exhaust does not exceed a set value and performs mixing the exhaust and air.

However, if clogging by scale is detected on the basis of elevation of the water temperature due to after-boiling after combustion has stopped, as with the device of Patent Document #1, then it is not possible to perform such detection during combustion operation, and, depending upon the relationship between the position where heat is applied and the position where the temperature sensor is attached, sometimes it may happen that, in the case of a combustion pattern in which the amount of combustion is low or in the case of a hot water supply device of high capacity, it becomes difficult to detect temperature elevation due to after-boiling. Furthermore there is the problem that setting the standard for determination of clogging by scale is not simple or easy, since it is necessary to check the relationship between clogging by scale and after-boiling for each pattern of combustion.

Moreover with the device of Patent Document #2 there is the problem that, since the determination as to whether clogging by scale is taking place is performed by varying the amount of combustion during combustion operation, accordingly fluctuations of the amount of hot water supply or of the hot water supply temperature that are not according to the intention of the user may occur. And, with the device of Patent Document #3, there is a danger that erroneous detection may occur, since the temperature of the combustion exhaust gas is estimated after heat exchange by the exhaust temperature estimation means based on the temperature of the previously heated water and the temperature of the output hot water. Yet further, with the device of Patent Document #4, although combustion control is performed by measuring the temperature of the combustion exhaust gas after heat exchange, no means is disclosed for determining whether or not clogging by scale has occurred.

The object of the present invention is to provide a hot water supply device that is capable of accurately determining whether or not clogging by scale has occurred.

SUMMARY OF THE INVENTION

The present invention presents a hot water supply device, comprising: a heat exchanger for applying heat to water with combustion gas, including a plurality of fins, a heat exchange tubing, and a heat exchanger case; a temperature detection means for detecting an exhaust temperature after heat exchange by the heat exchanger; and a determination means that determines that scale is deposited inside the heat exchange tubing of the heat exchanger if the exhaust temperature detected by the temperature detection means is higher than a set temperature.

In a preferable first aspect of the present invention, the temperature detection means is disposed in a neighborhood of the fins which are in contact with exhausted combustion gas that passes surroundings of a heat exchange tubing portion on a downstream side among heat exchange tubing portions, in the heat exchange tubing constituting the heat exchanger, which are closest to a combustion portion where combustion always takes place during hot water supply operation.

In a preferable second aspect of the present invention, the heat exchanger is a sensible heat exchanger for recovering sensible heat in the combustion gas, and further comprises a latent heat exchanger for recovering latent heat in the combustion gas at a downstream side of a combustion gas flow of the sensible heat exchanger.

In a preferable third aspect of the present invention, the heat exchanger is a sensible heat exchanger for recovering sensible heat in the combustion gas, and further comprises a latent heat exchanger for recovering latent heat in the combustion gas at the downstream side of a combustion gas flow of the sensible heat exchanger; and the temperature detection means is disposed in an exhaust flow between the sensible heat exchanger and the latent heat exchanger.

In a preferable fourth aspect of the present invention, the heat exchanger is a sensible heat exchanger for recovering sensible heat in the combustion gas, and further comprises a latent heat exchanger for recovering latent heat in the combustion gas at a downstream side of a combustion gas flow of the sensible heat exchanger.

In a preferable fifth aspect of the present invention, the heat exchanger is a sensible heat exchanger for recovering sensible heat in the combustion gas, and further comprises a latenheat exchanger for recovering latent heat in the combustion gas at the downstream side of a combustion gas flow of the sensible heat exchanger; and the temperature detection means is disposed in an exhaust passage between the sensible heat exchanger and the latent heat exchanger.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a rough structural drawing showing a hot water supply device according to an embodiment of the present invention;

FIG. 2 is an elevation view of the hot water supply device;

FIG. 3 is a vertically sectional view of the hot water supply device;

FIG. 4 is an enlarged vertically sectional view of a portion to which a temperature detection means is provided;

FIG. 5 is a plan view of an essential portion of a lower heat exchange region of a heat exchanger section;

FIG. 6 is a plan view of an essential portion of an upper heat exchange region of the heat exchanger section; and

FIG. 7 is a flow chart of operational control for reaching a decision as to whether or not clogging by scale has occurred.

DETAILED DESCRIPTION

Hereinafter, embodiments for implementing the present invention will be explained on the basis of the following description.

First, the overall structure of a hot water supply device 1 according to the present invention will be explained.

The hot water supply device 1 is employed as a supply of heat such as a hot water supply device or a room heating device or the like, and, as shown in FIG. 1, is a gas-powered hot water supply device that supplies hot water by utilizing application of heat generated by combustion of fuel gas to cold water or to warm water.

This hot water supply device 1 comprises an air blower fan 2 that supplies air for combustion, a burner section 3 that combusts fuel gas, a heat exchanger section 4 that exchanges heat between the combustion gases from the burner section 3 and water, an exhaust aperture 5 that discharges the combustion gases after heat exchange by the heat exchanger section 4, conduits of various types such as a cold water intake pipe 6 a and a hot water outlet pipe 6 b and so on, and a control unit 7 that receives signals from sensors of various types and performs operational control for devices of various types.

First, the burner section 3 will be explained.

The burner section 3 comprises a burner unit 11 that mixes together fuel gas supplied from a fuel supply conduit (not shown in the figures) and air for combustion supplied by the air blower fan 2 and that combusts the resulting mixture, a burner casing 12 that contains the burner unit 11, a combustion space 13 within the burner casing 12 above the burner unit 11, and so on. The burner casing 12 is formed in the shape of a rectangular parallelepiped whose top is open. The air blower fan 2 is disposed in the lower end portion of the burner casing 12.

As shown in FIGS. 1, 2, 5, and 6, the burner unit 11 includes a plurality of combustion tubes 14 that are arranged in sequence along the left to right direction in the figures, and, for example, may be built in a multi-stage structure consisting of three combustion stages 11 a through 11 c. The combustion stages 11 a through 11 c include, for example, five, two, and three combustion tubes 14 respectively, and are connected to corresponding fuel supply conduits. In this configuration, combustion by each of the combustion stages 11 a through 11 c can be controlled individually by the control unit 7, and, according to various types of operation, which of the combustion stages 11 a through 11 c are actually operated for combustion, and their heat output, may be adjusted.

For example, during operation to supply hot water, the combustion operation may be changed over between four combustion stages: a first combustion phase in which only the two combustion tubes 14 of the central combustion stage 11 b are operated for combustion; a second combustion phase in which the five combustion tubes 14 of the central combustion stage 11 b and of the right side combustion stage 11 c are operated for combustion; a third combustion phase in which the seven combustion tubes 14 of the left side combustion stage 11 a and of the central combustion stage 11 b are operated for combustion; and a fourth combustion phase in which all of the ten combustion tubes 14 of all of the combustion stages 11 a through 11 c are operated for combustion. It should be understood that the central combustion stage 11 b corresponds to the combustion portion where combustion is always performed during operation to supply hot water.

As shown in FIGS. 2 and 3, an igniter 15 and a flame rod 16 are disposed within the combustion space 13, above the portion that corresponds to the combustion stage 11 b of the burner unit 11. The igniter 15 and the flame rod 16 are both attached from the front surface of the burner casing 12, and the flame rod 16 is provided on the right side of the igniter 15.

The igniter 15 is a device for igniting the fuel-air mixture gases supplied from the burner unit 11 by generating an ignition spark between itself and an ignition target provided to the burner unit 11, and is attached so as to project into the combustion space 13 and moreover so as to extend slantingly downward.

And the flame rod 16 is a device for applying a voltage to the flame during combustion operation of the burner unit 11 and for employing conductivity and rectification due to ionization of the flame in order to detect the presence or absence of a flame by detecting electrical current flowing from the flame rod 16 to the flame, and is attached so as to project into the combustion space 13 and so as to extend approximately horizontally.

Next, the heat exchanger section 4 will be explained.

As shown in FIGS. 1 through 3, the heat exchanger section 4 comprises a sensible heat exchanger 17 that mainly recovers sensible heat in the combustion gases, a latent heat exchanger 19 that mainly recovers latent heat from the combustion gases (i.e. from the exhaust) after heat exchange has been performed by the above sensible heat exchanger 17, a lower heat exchanger case 18 that contains the sensible heat exchanger 17, an upper heat exchanger case 20 that contains the latent heat exchanger 19, and so on.

In plan view, the lower heat exchanger case 18 is built in the shape of a rectangular frame in plan view, with the lower end portion of the lower heat exchanger case 18 and the upper end portion of the burner casing 12 being joined together by caulking or by screwing.

And the upper heat exchanger case 20 is built in the shape of a rectangular parallelepiped, having a tray 6 d at its lower end portion, i.e. its bottom portion, that recovers drained water (i.e. condensed water) generated by recovery of latent heat, with an exhaust outlet 24 being formed in the lower heat exchanger case 18 and constituting an outlet therefrom for the exhaust and opening toward the interior of the upper heat exchanger case 20, and moreover with the exhaust aperture 5 that discharges the exhaust after heat exchange to the exterior of the hot water supply device 1 being provided on the front surface of the hot water supply device 1, at a lower portion of the front surface of the upper heat exchanger case 20.

The lower end portion of the upper heat exchanger case 20 and the upper end portion of the lower heat exchanger case 18 are joined together by caulking or by screwing. And, as shown in FIGS. 2 and 3, a temperature fuse 23 that is capable of detecting anomalously high temperature is provided at the outer portion of the lower heat exchanger case 18.

Next, the sensible heat exchanger 17 will be explained. As shown in FIGS. 3, 5, and 6, the sensible heat exchanger 17 is built as a fin and tube type heat exchanger, and comprises a heat exchange tubing 25 and a plurality of fins 26 that are fixed to the heat exchange tubing 25 so as to be capable of heat transfer. The plurality of fins 26 are all brazed to the heat exchange tubing 25 and the inner peripheral surface of the lower heat exchanger case 18. The heat exchange tubing 25 and the fins 26 are made from copper, but this material is not necessarily particularly limited; they could also be made from stainless steel.

As shown in FIGS. 1, 3, 5, and 6, a heat exchange region 21 in the interior of the lower heat exchanger case 18 of the sensible heat exchanger 17 has a two-stage structure, and includes a lower heat exchange region 21A on the lower side thereof facing the combustion space 13, and an upper heat exchange region 21B on the upper side thereof (i.e. on the downstream side of the combustion gas flow). It should be understood that the numeral “F” shown in the drawing shows the front, the numeral “L” shows the left, the numeral “W” shows the cold water inlet, and the numeral “HW” shows the hot water exit.

As shown in FIGS. 5 and 6, the heat exchange tubing 25 comprises a plurality of straight tube portions 27 that are arranged approximately in parallel through two stages, and a plurality of curved link tube portions 28 that connect together the end portions of the plurality of straight tube portions 27. Four of the straight tube portions 27 are provided in the lower heat exchange region 21A shown in FIG. 5, and four of the straight tube portions 27 are provided in the upper heat exchange region 21B shown in FIG. 6; and, in plan view, the heat exchange tubing 25 is built in a snaking shape in each of the lower heat exchange region 21A and the upper heat exchange region 21B. And the downstream side end portion of the straight tube portion 27 b at the downstream side of the lower heat exchange region 21A is connected by a curved link tube portion 28 to the upstream side end portion of the straight tube portion 27 c at the upstream side of the upper heat exchange region 21B.

Along with fuel gas being supplied from the fuel supply conduit to the burner unit 11, air for combustion is also supplied from the air blower fan 2, and the fuel-air mixture gases that has been produced by mixing the fuel gas and the combustion air in the combustion space 13 is combusted therein. The combustion gases that is generated at this time flows into the interior of the lower heat exchanger case 18 which is above the combustion space 13, and its temperature drops as it transfers heat to fresh water in the sensible heat exchanger 17, and then the combustion gases is exhausted from the exhaust outlet 24 of the lower heat exchanger case 18 and flows into the interior of the upper heat exchanger case 20.

After the fresh water that has flowed into the sensible heat exchanger 17 has flowed though the lower heat exchange region 21A of the heat exchange tubing 25, it flows into the upper heat exchange region 21B and heat is supplied to this fresh water due to the sensible heat of the combustion gases while it passes through the sensible heat exchanger 17 as described above, and then it flows out from the hot water outlet pipe 6 b to the exterior of the hot water supply device 1 as hot water.

Next, the latent heat exchanger 19 will be explained. As shown in FIG. 3, in the latent heat exchanger 19, a plurality of heat transfer tubes 29 are provided in a spiral shape or in a snaking shape in the interior of the upper heat exchanger case 20.

Flow rectifying plates 31 a, 31 b, 31 c are provided in the interior of the upper heat exchanger case 20 so as to define flow passage and to rectify the flow of the combustion gases flowing from the exhaust outlet 24 into the interior of the upper heat exchanger case 20, with combustion gases being discharged from the exhaust aperture 5 that is provided at the front side of the upper heat exchanger case 20 to the exterior of the hot water supply device 1 after heat exchange has been performed. At this time, along with the temperature of the combustion gases being lowered by supplying heat to the fresh water that is supplied from the fresh water supply to the cold water intake pipe 6 a of the latent heat exchanger 19, also water vapor included in the combustion gases condenses and becomes drain water (condensed water) and is collected in the tray 6 d, and is sent to a neutralizer via a drain pipe 6 c, then being neutralized and discharged to the exterior of the hot water supply device 1. The fresh water to which heat has thus been supplied flows to the straight tube portion 27 a at the upstream side of the lower heat exchange region 21A of the sensible heat exchanger 17.

Next, the temperature detection sensor 32 will be explained on the basis of FIGS. 3, 4, 5, and 6. As shown in FIG. 3, the hot water supply device 1 comprises the temperature detection sensor 32, which is a temperature detection means that detects the temperature of the combustion gases (i.e. the exhaust temperature) after heat exchange in the sensible heat exchanger 17. In the heat exchange tubing 25 of the sensible heat exchanger 17 shown in FIGS. 5 and 6, the temperature detection sensor 32 is disposed in the neighborhood of the fins 26 which are in contact with the exhausted combustion gases that passes surroundings of a heat exchange tubing portion on a downstream side among the heat exchange tubing portions, in the heat exchange tubing constituting the heat exchanger, which are closest to the combustion stage 11 b that always performs combustion during hot water supply operation.

As shown in FIG. 4, the temperature detection sensor 32 is inserted from the rear side of the upper heat exchanger case 20 so as to be inserted in the neighborhood of the fins 26 that are fixed to the portion, in the straight tube portion 27 b that is furthest toward the downstream side of the lower heat exchange region 21A, that is directly above the combustion stage 11 b, and is fixed to the upper heat exchanger case 20 by brazing.

The temperature detection sensor 32 is a per se known temperature detection sensor comprising a thermocouple 32 a, a pair of lead wires 32 b that extend from the thermocouple 32 a, and so on. The pair of lead wires 32 are connected to the control unit 7, and thereby the exhaust temperature of the combustion gases that is discharged from the lower heat exchanger case 18 is transmitted to the control unit 7 by the detection signal from the temperature detection sensor 32

Next, the control unit 7 will be explained.

The control unit 7 shown in FIGS. 1 and 2 is a device for performing control of the hot water supply device 1, and various sensors are electrically connected thereto, so that it can receive the detection signals from these various sensors. The control unit 7 controls the operation of the air blower fan 2 and of the burner unit 11 for performing hot water supply operation, on the basis of the hot water supply temperature that has been set by remote control operation or the like, the amount of hot water that is to be supplied to a hot water supply faucet, detection signals that have been received from various sensors, and so on.

Next, the operational control for determining clogging by scale will be explained.

As shown in FIG. 7, the control unit 7, which corresponds to the determination means, is capable of executing scale clogging determination operational control, in which it is determined that scale is deposited inside the heat exchange tubing 25 of the sensible heat exchanger 17 if the exhaust temperature detected by the temperature detection sensor 32 is higher than a set temperature. This control program for scale clogging determination operational control is stored in advance in the control unit 7. It should be understood that, in the following, the reference symbols Si (where i=1, 2, . . . ) in the figure refer to corresponding steps.

Initially, in step S1, the control unit 7 makes a determination as to whether or not the hot water supply device 1 is currently performing supply of hot water. If the hot water supply device 1 is currently supplying hot water, in other words if the control unit 7 receives a signal that hot water supply is being performed, then the result of the determination in step S1 is affirmative and the flow of control proceeds to step S2, whereas step S1 is repeated while the result of the determination in step S1 is negative.

Next, in step S2, the control unit 7 acquires the temperature of the exhaust by reading in the detection signal from the temperature detection sensor 32 that measures the exhaust temperature, and then the flow of control proceeds to step S3.

Next, in step S3, a determination is made as to whether or not the exhaust temperature is higher than a set temperature (for example, around 180° C. to 200° C.), and, if the exhaust temperature is higher than the set temperature, then an affirmative determination is reached in this step S3, and the flow of control proceeds to step S4. But if the exhaust temperature is not higher than the set temperature, then a negative determination is reached in this step S3 and it is determined that the sensible heat exchanger 17 is in its normal state, so that the flow of control returns. It should be understood that the set temperature need not necessarily be limited to the temperature range described above; it could be varied as appropriate.

Here, during operation for supplying hot water, as described above, although combustion operation is performed while adjusting the burner unit 11 in four stages according to the requested heat amount, the two combustion tubes 14 of the center combustion stage 11 b are capable of combustion operation at the minimum combustion level, and accordingly, during operation for supplying hot water, they are always performing combustion.

On the other hand, in the sensible heat exchanger 17, since the fresh water to which heat has been transferred by the latent heat exchanger 19 and that is supplied to the heat exchange tubing 25 flows in a snaking manner from the straight tube portion 27 a on the upstream side of the lower heat exchange region 21A toward the straight tube portion 27 b on its downstream side while heat is supplied thereto, and since the temperature of the water in the straight tube portion 27 b becomes higher than the water temperature in the straight tube portion 27 a, the temperature of the straight tube portion 27 b of the lower heat exchange region 21A which is closest to the burner unit 11 becomes the highest.

Due to this, scale can more easily be deposited in the portion of the straight tube portion 27 b that is directly above the combustion stage 11 b in which combustion always takes place, as compared to the other portions. If clogging by scale occurs in the straight tube portion 27 b, then the temperature of the exhaust discharged from the lower heat exchanger case 18 rises abnormally to around 180° C. to 200° C., because the heat transfer by the sensible heat exchanger 17 becomes poor. Since the exhaust temperature is normally maintained at around 120° C. if the sensible heat exchanger 17 is in its normal condition (i.e. is not clogged by scale), accordingly, by taking advantage of this elevation of the exhaust temperature, it is possible to determine accurately upon the fact that clogging by scale has occurred.

In step S4, the control unit 7 determines that clogging by scale of the sensible heat exchanger 17 has occurred, and notifies the user of this fact via a display on a remote operation control, or by audio or the like; and then the flow of control returns. It should be understood that it may be arranged, after this notification of clogging by scale, to continue the operation for supplying hot water; or it may be arranged to stop the operation for supplying hot water directly after the notification of clogging by scale; or it may be arranged to stop the operation for supplying hot water after a predetermined time period has elapsed after the notification of clogging by scale.

Next, the operation and the beneficial effects of the hot water supply device 1 of the present invention will be explained.

Since the hot water supply device 1 of the present invention includes the temperature detection sensor 32 for detecting the exhaust temperature and the control unit 7 that determines that scale is deposited inside the heat exchange tubing 25 of the sensible heat exchanger 17 when the temperature detected by the temperature detection sensor 32 has become higher than the set temperature, accordingly it is possible to detect elevation of the exhaust temperature arising from hampering of heat exchange in the sensible heat exchanger 17 due to clogging by scale, and it is possible accurately to determine that clogging by scale of the sensible heat exchanger 17 has occurred if the exhaust temperature has become higher than the set temperature.

In other words, since the control unit 7 detects clogging by scale by directly detecting the exhaust temperature during combustion operation with the temperature detection sensor 32, and by detecting anomalous elevation of the exhaust temperature, accordingly it is possible accurately to determine upon clogging by scale even during combustion operation, which is different from the case with a hot water supply device that determines upon clogging by scale from increase of the water temperature after combustion has stopped or from change of the heat exchange efficiency during combustion operation, and from the case with a device that determines upon clogging by scale by estimating the exhaust temperature; and as a result, when making the determination as to whether clogging by scale has occurred, it is possible to prevent fluctuations of the hot water supply amount or of the temperature of the hot water that are not intended by the user.

Furthermore, since the temperature detection sensor 32 is provided in the heat exchange tubing 25 incorporated in the sensible heat exchanger 17, and is located in the neighborhood of the fins 26 where combustion gases is exhausted that has passed the surroundings of the downstream side of that heat exchange tubing portion that is closest to the combustion stage 11 b in which combustion always takes place during operation to supply hot water, accordingly it is possible to detect the exhaust temperature of the combustion gases that has passed the heat exchange tubing portion in which clogging by scale can most easily occur, irrespective of the pattern of combustion in the burner unit 11, and thus it is possible to cope with combustion operation by the burner unit 11 at the minimum combustion amount.

Yet further, since the latent heat exchanger 19 is provided that retrieves latent heat in the es on the downstream side of the combustion gas flow of the sensible heat exchanger 17, accordingly, along with it being possible to provide a hot water supply device 1 having high efficiency that is capable of utilizing the greater portion of the heat generated by combustion for application to fresh water, also, although the heat exchange efficiency of the sensible heat exchanger 17 may be reduced due to the adherence of scale within the range of permitted exhaust temperature, still it is possible to determine upon clogging by scale in an accurate manner, even with this structure in which the decrease of the heat exchange efficiency of the hot water supply device as a whole is reduced since heat is applied to the fresh water by the latent heat exchanger 19, since the exhaust temperature is detected directly after heat exchange has been performed by the sensible heat exchanger 17.

Next, modified embodiments in which the embodiment described above is partially varied will be explained.

[1] While the temperature detection sensor 32 of the embodiment described above is inserted so as to be approximately horizontal, it would also be acceptable for the temperature detection sensor 32 to be inserted and fixed sloping downward so as to approach the corresponding fin, in order to reduce the influence of exhaust being mixed in from combustion sections other than the combustion section where combustion always takes place during the supply of hot water; and it would also be acceptable for the temperature detection sensor 32 to be inserted and fixed in a state in which the end of the sensor 32 is bent downward so as to be close to the fin.

[2] While, in the embodiment described above, the thermocouple 32 a was employed as the temperature sensor 32, this should not be considered as being necessarily limitative; it would also be possible to employ a temperature sensor that includes a thermistor.

[3] Although the burner unit 11 of the embodiment described above was built as a multi-stage burner having the ten combustion tubes 14 and including the three combustion stages 11 a through 11 c, the present invention is not necessarily limited to this particular construction; the number of combustion stages of the burner unit and the numbers of combustion tubes in the various combustion stages may be varied as appropriate.

[4] While the hot water supply device 1 of the embodiment described above was a hot water supply device of the upward proceeding combustion type in which the heat exchanger section 4 was provided above the burner section 3, it would also be possible to implement the present invention as a hot water supply device of the downward proceeding combustion type, in which the up and down directions are approximately opposite.

[5] Apart from the above, it would be possible for various changes or additions to be implemented to the above described embodiment of the present invention by a person skilled in the art, provided that the gist of the present invention is preserved; and the present invention is to be understood as also including such changes and additions. 

1. A hot water supply device, comprising: a heat exchanger for applying heat to water with combustion gas, including a plurality of fins, a heat exchange tubing, and a heat exchanger case; a temperature detection means for detecting an exhaust temperature after heat exchange by the heat exchanger; and a determination means that determines that scale is deposited inside the heat exchange tubing of the heat exchanger if the exhaust temperature detected by the temperature detection means is higher than a set temperature.
 2. A hot water supply device according to claim 1, wherein the temperature detection means is disposed in a neighborhood of the fins which are in contact with exhausted combustion gas that passes surroundings of a heat exchange tubing portion on a downstream side among the heat exchange tubing portions, in the heat exchange tubing constituting the heat exchanger, which are closest to a combustion portion where combustion always takes place during hot water supply operation.
 3. A hot water supply device according to claim 1, that is a latent heat recovery type hot water supply device, wherein the heat exchanger is a sensible heat exchanger for recovering sensible heat in the combustion gas, and further comprises a latent heat exchanger for recovering latent heat in the combustion gas at a downstream side of a combustion gas flow of the sensible heat exchanger.
 4. A hot water supply device according to claim 1, that is a latent heat recovery type hot water supply device, wherein the heat exchanger is a sensible heat exchanger for recovering sensible heat in the combustion gas, and further comprises a latent heat exchanger for recovering latent heat in the combustion gas at the downstream side of a combustion gas flow of the sensible heat exchanger; and wherein the temperature detection means is disposed in an exhaust passage between the sensible heat exchanger and the latent heat exchanger.
 5. A hot water supply device according to claim 2, that is a latent heat recovery type hot water supply device, wherein the heat exchanger is a sensible heat exchanger for recovering sensible heat in the combustion gas, and further comprises a latent heat exchanger for recovering latent heat in the combustion gas at a downstream side of a combustion gas flow of the sensible heat exchanger.
 6. A hot water supply device according to claim 2, that is a latent heat recovery type hot water supply device, wherein the heat exchanger is a sensible heat exchanger for recovering sensible heat in the combustion gas, and further comprises a latenheat exchanger for recovering latent heat in the combustion gas at the downstream side of a combustion gas flow of the sensible heat exchanger; and wherein the temperature detection means is disposed in an exhaust passage between the sensible heat exchanger and the latent heat exchanger. 